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Mixed Result for Bone Drug in Cancer Study

The results of a new study are tempering hopes that a drug used to treat bone loss might also help stave off relapses of breast cancer, especially for younger women, researchers said Thursday.

The clinical trial found that women with early breast cancer who were treated with the bone drug zoledronic acid did not have fewer recurrences of their cancer than women who did not receive the drug. The results surprised and disappointed some experts because they conflicted with the findings of a previous, widely publicized trial.

“Most people in the breast cancer community were very hopeful that this would be a positive study,” Dr. Sharon Giordano of the M. D. Anderson Cancer Center in Houston said in an interview. She was not involved in the study but is to deliver a commentary about it on Friday at the San Antonio Breast Cancer Symposium, where the results will be presented.

Still, Dr. Giordano and others said the latest results would not be the final word because additional studies were under way. Moreover, the new study suggested that the bone drug could help stave off recurrences for women well past menopause.

Zoledronic acid, sold by Novartis under the name Zometa, is one of a class of bone drugs known as bisphosphonates. It is approved to prevent fractures and other skeletal problems that can occur when breast cancer or other tumors spread to the bone.

A leading theory for that effect was that the breakdown of bone provided substances that stimulate tumor growth. Drugs that slow that breakdown deprive tumors of those substances.

But the new study contradicts those findings. This study involved 3,360 patients, mainly in Britain, who had their breast tumors removed by surgery and underwent whatever chemotherapy or other treatment their physicians chose to prevent recurrence. Half the patients also received intravenous infusions of zoledronic acid for five years.

After nearly five years, the number of women who had had a recurrence or had died without a recurrence was about the same — 403 in the control group and 404 in the group receiving zoledronic acid. Those receiving the bone drug had a somewhat lower risk of dying, but the difference was not statistically significant.

However, the bone drug did seem to help women in the study who were at least five years past menopause, who accounted for about 30 percent of the participants. Among these women, there were 116 recurrences for those who got zoledronic acid compared with 147 in the control group, a risk reduction of 27 percent. Their risk of death was reduced 29 percent, with 86 deaths among those who got the drug compared with 120 deaths in the control group.

Dr. Robert E. Coleman of the University of Sheffield in England, the lead investigator of the study, said this suggested that zoledronic acid could help prevent relapse or spread only in the absence of estrogen or some other substance no longer produced by postmenopausal women.

In the study from nearly two years ago, the 1,800 participants were all premenopausal but were given a drug that shut down their ovaries, preventing them from making estrogen.

Dr. Michael Gnant of the Medical University of Vienna, who was the lead investigator of the earlier study, said at a news conference at the San Antonio symposium that the new results strengthened his belief in zoledronic acid.

But Dr. Giordano said that conclusions based on a subset of patients must be regarded with caution and that they should not change medical practice. She and others said there were other differences between the trials that might explain the divergent outcomes.

One thing experts agreed on was that zoledronic acid should now not be given to younger women with functioning ovaries unless the cancer had spread to their bones. That is true not only because the new trial showed no cancer benefit for these women but also because the drug can destroy jawbones in some patients.

The new study was sponsored by the University of Sheffield. Dr. Coleman and Dr. Gnant are paid consultants for Novartis, which contributed some money.

Just last week, a study published in The Lancet showed that zoledronic acid reduced the risk of disease progression and improved survival in patients with multiple myeloma, a cancer of the bone marrow.

A version of this article appears in print on December 10, 2010, on page A19 of the New York edition with the headline: Mixed Result for Bone Drug in Cancer Study. Order Reprints|Today's Paper|Subscribe